The current mainstream in the semiconductor industry is the manufacture of semiconductor devices in resin-encapsulated form including diodes, transistors, IC's, LSI's, and super LSI's. A steadily increasing demand is expected for them. As semiconductor devices progressively increase their degree of integration, the chip size is also increased. Nevertheless packages are desired to have as small dimensions as possible. Semiconductor devices are now commercially available in thin compact packages irrespective of larger chips.
Such thin compact packages of semiconductor devices with larger chips are then assembled on printed circuit boards. One common practice is to dip the packages in a solder bath or pass the packages through a hot zone where solder melts, ensuring the automated connection of the semiconductor devices to the printed circuit boards. However, when thin compact packages of semiconductor devices with larger chips are dipped in solder bath or exposed to a solder-melting hot zone, the resulting thermal shock would often cause the encapsulating resin to crack, losing the reliability of semiconductor devices. Occurrence of cracks in the encapsulating resin becomes frequent when the resin contains moisture. Since it is unavoidable in the actual manufacturing process that the encapsulating resin absorbs moisture, the crack occurrence creates a serious problem in the actual assembly operation.